/*=========================================================================

  Program:   Visualization Toolkit
  Module:    vtkGeoSource.h

  Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
  All rights reserved.
  See Copyright.txt or http://www.kitware.com/Copyright.htm for details.

     This software is distributed WITHOUT ANY WARRANTY; without even
     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
     PURPOSE.  See the above copyright notice for more information.

=========================================================================*/
/*-------------------------------------------------------------------------
  Copyright 2008 Sandia Corporation.
  Under the terms of Contract DE-AC04-94AL85000 with Sandia Corporation,
  the U.S. Government retains certain rights in this software.
-------------------------------------------------------------------------*/
/**
 * @class   vtkGeoSource
 * @brief   A multi-resolution geographic data source
 *
 *
 * vtkGeoSource is an abstract superclass for all multi-resolution data sources
 * shown in a geographic view like vtkGeoView or vtkGeoView2D. vtkGeoSource
 * subclasses need to implement the FetchRoot() method, which fills a
 * vtkGeoTreeNode with the low-res data at the root, and FetchChild(), which
 * produces a refinement of a parent node. Other geovis classes such as
 * vtkGeoTerrain, vtkGeoTerrain2D, and vtkGeoAlignedImageSource use a
 * vtkGeoSource subclass to build their geometry or image caches which are
 * stored in trees. The source itself does not maintain the tree, but
 * simply provides a mechanism for generating refined tree nodes.
 *
 * Sources are multi-threaded. Each source may have one or more worker threads
 * associated with it, which this superclass manages. It is essential that the
 * FetchChild() method is thread-safe, since it may be called from multiple
 * workers simultaneously.
*/

#ifndef vtkGeoSource_h
#define vtkGeoSource_h

#include "vtkGeovisCoreModule.h" // For export macro
#include "vtkObject.h"

class vtkAbstractTransform;
class vtkCollection;
class vtkConditionVariable;
class vtkGeoTreeNode;
class vtkMultiThreader;
class vtkMutexLock;

class VTKGEOVISCORE_EXPORT vtkGeoSource : public vtkObject
{
public:
  vtkTypeMacro(vtkGeoSource,vtkObject);

  vtkGeoSource();
  ~vtkGeoSource() override;

  //@{
  /**
   * Blocking access methods to be implemented in subclasses.
   */
  virtual bool FetchRoot(vtkGeoTreeNode* root) = 0;
  virtual bool FetchChild(vtkGeoTreeNode* node, int index, vtkGeoTreeNode* child) = 0;
  //@}

  //@{
  /**
   * Non-blocking methods for to use from the main application.
   * After calling RequestChildren() for a certain node,
   * GetRequestedNodes() will after a certain period of time return a
   * non-null pointer to a collection of four vtkGeoTreeNode objects,
   * which are the four children of the requested node.
   * The collection is reference counted, so you need to eventually
   * call Delete() on the returned collection pointer (if it is non-null).
   */
  virtual void RequestChildren(vtkGeoTreeNode* node);
  virtual vtkCollection* GetRequestedNodes(vtkGeoTreeNode* node);
  //@}

  /**
   * Spawn worker threads.
   */
  void Initialize(int numThreads = 1);

  /**
   * Shut down the source. This terminates the thread and releases memory.
   */
  void ShutDown();

  void WorkerThread();

  /**
   * Return the projection transformation used by this source.
   */
  virtual vtkAbstractTransform* GetTransform() { return nullptr; }

protected:

  vtkCollection* InputSet;
  vtkCollection* ProcessingSet;

  //@{
  /**
   * Locks the set for reading or writing
   */
  vtkMutexLock* InputSetLock;
  vtkMutexLock* ProcessingSetLock;
  vtkMutexLock* OutputSetLock;
  //@}

  vtkMutexLock* Lock;

  vtkConditionVariable* Condition;

  vtkMultiThreader* Threader;
  bool StopThread;
  bool Initialized;

  class implementation;
  implementation* Implementation;

private:
  vtkGeoSource(const vtkGeoSource&) = delete;
  void operator=(const vtkGeoSource&) = delete;
};

#endif // vtkGeoSource_h